AUDITORIUM:

A CASE STUDY ON ACOUSTIC DESIGN

BUILDING SCIENCE II

ARC3413/BLD61303

SEMESTER 5

BACHELOR OF SCIENCE (HONS) IN ARCHITECTURE

SCHOOL OF ARCHITECTURE BUILDING AND DESIGN

LECTURER: MR. AZIM SULAIMAN

GROUP MEMBERS:

ALAN KOO

CANISIUS BONG

JOYCE WEE

KAN SOOK SAN

LIEW JIN

LUM SI CHU

MAXIMILIAN LIM

ONG EUXUAN

RICCO SOH

0318757

0318914

0319602

0319326

0318449

0319502

0319604

0319050

0319890

2

TABLE OF CONTENT

INTRODUCTION ……………………………………………………..3

Historical Background - Organization

- Building

Auditorium

DRAWINGS………………………………………………………….6

Plans

Section

SOUND ABSORPTION………………………………………………...9

Finishing Materials - Floors

- Walls

- Ceilings

- Seats

Acoustic Wall Panelling / Treatment - Stretched Fabric Panels

- Hardwood Wall Slats

SOUND SOURCE………………………………………………….….18

Sound Systems - Single Speaker Cabinets

- Line Array Speakers

- Stage Monitors

Noise Intrusion Areas

SOUND PATH / PROPOGATION………………………………………25

Sound Shadow Area

Sound Reflection - Ceilings

- Walls

Sound Diffraction

REVERBERATION TIME……………………………………………..33

3

INTRODUCTION

HISTORICAL BACKGROUND

4

Organization: Sidang Injil Borneo Kuala Lumpur (SIBKL)

As one of the most established protestant churches in Malaysia, Sidang Injil Borneo was started in

Sarawak, and has been around for nearly ninety years. In 1999, SIBKL became a cell church for the

Sidang Injil Borneo, and operates more than 90 cell groups for people of all ages across the region.

Case Study Location: Bangunan Yin, Jalan Damansara

Weekly Sunday sessions of SIBKL are carried out every Sunday in Bangunan Yin, located in Phileo

Damansara, Petaling Jaya. Bangunan Yin is a multi-storey building that houses the church, as well as

smaller offices during the weekdays.

AUDITORIUM

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SIBKL Auditorium, Bangunan Yin, Jalan Damansara

Type of Auditorium: Multipurpose (Speech and Music)

Shape: Fan-shaped

Total Volume: 11393 m3

Total Floor Area: 2120 sqm

Year of Completion:

Sunday sessions and church events are carried out in the auditorium of Bangunan Yin, located on the

fifth and sixth floor of the building. The auditorium has two floors, and has a seating capacity for more

than 1500 people. It has a fan-shaped balcony that hovers over the auditorium, multiplying its space,

allowing the auditorium to hold more audience.

6

DRAWINGS

Floor Plans

Fifth Floor Plan of Bangunan Yin

7

Sixth Floor Plan of Bangunan Yin

SECTIONS

8

Sections of Bangunan Yin

9

SOUND ABSORPTION

Sound absorption is defined as the change in sound energy into heat energy, as the incident sound that

strikes a material that is not reflected back. It is also one of the major factors in creating good acoustic

space, especially when controlling reverberation. Soft and porous materials like fabrics serve as good

acoustic insulators which means it absorbs most of the sound.

Finishing Materials

Floor

10

Location of carpeted floor on auditorium plans

Material: Carpet (Porous Absorber)

Absorption coefficient for thick pile carpet: 0.50

Carpet is the antithesis of hard, echoing surfaces. Sound waves are effectively absorbed and deflected

by the carpet and by the padding under the carpet, and the level of sound absorption can be enhanced

with a thicker pad.

Walls

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Material 1: Fabric

Absorption coefficient for fabric: 0.90

The walls of the auditorium is covered with fabric wrapped wall panels. These wall panels serve to

reduce echo and reverberation in the auditorium, improving the intelligibility of sound within the space.

Material 2: Timber Hardwood

Absorption coefficient for Belian timber hardwood: 0.42

Timber is also greatly used on wall slats in the auditorium. Its reflective nature performs strongly for

acoustics. Due to internal friction within the substructure of wood, timber has a strong sound dampening

capacity, allowing to control its echo and reverberation by reducing the transmission of sound vibration.

Ceiling

12

Location of timber finishing on auditorium reflected ceiling plans

Material 1: Timber Hardwood

Absorption coefficient for timber hardwood: 0.42

The ceilings of the auditorium are lined with timber convex reflective surfaces. Parts of the ceilings are

also comprised of strips of timber slats. Timber is reflective and has a strong sound dampening capacity.

13

Location of gypsum boards on auditorium reflected ceiling plans

Material 2: Gypsum Board

Absorption coefficient for plaster board: 0.08

Gypsum board is a plasterboard panel material. It is constructed with joints and fastener heads that will

eventually be covered with a joint compound system to create a continuous surface for ceilings and

walls. In the case of this auditorium, it is used to produce edges and concave surfaces that would help

with the reflection of sound.

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Seats

Location of cushioned seatings on auditorium plans

Material: Cushioned Fabric Seatings (Porous Absorber)

Absorption coefficient for cushion fabric: 0.64

There is a total of 1584 cushioned seats in the auditorium (1117 seats at the bottom seating region, 467

seats on the balcony’s upper seating region).

To make the hearing conditions satisfactory when the room is full or partly full, upholstered seats with

absorbing material at the bottom are used, so that the absence or presence of audience does not affect

the reverberation time.

15

Acoustic Wall Panelling / Treatment

This auditorium installed individual panels of slit wooden resonators that alternate between stretched

fabric panels on its walls to maximize the sound absorbing quality of the space.

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Stretched Fabric Panels

Material 1: Stretched Fabric Panels (Membrane Absorber)

These wall panels are used to reduce echo and reverberation in the auditorium. They are constructed

from a rigid acoustical board, and are covered with acoustically transparent fabrics. The fabric on the

panels help to reduce echo and reverberation.

Advantages of fabric wrapped panel absorber:

- Maximize absorption of broadband sound frequencies, from 40 Hz to 20 kHz.

- Reduce excessive reverberation, flutter echo and primary reflections, increasing the

intelligibility of speech and clarity of sound.

- Easy installation

- Impact resistant, sturdy, lightweight construction

- Easy maintenance

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Hardwood Wall Slats

Materials: Hardwood Wall Slats (Cavity Absorber)

Beyond the cavities of the wall panels are narrow necks that lead down to air spaces. The enclosed body

of air are contained within these rigid panels. The sound that propagates within the auditorium will be

trapped in these air spaces to reduce sound reflection within the space.

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SOUND SOURCE

Sound source is the source of where sound waves are generated. It creates vibrations in the

surrounding medium, allowing them to propagate. Generally, within an auditorium, the source of

sound is usually the sound system speakers.

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Sound Systems

A typical sound system in an auditorium may include a combination of microphones, signal processors,

amplifiers and loudspeakers in speaker cabinets. These systems reinforce sound to enhance its volume,

then distribute it to a larger audience.

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The sound system in the auditorium is controlled by an audio mixing board that makes live sounds

louder, and also distributes those sounds to a wider audience. It may also enhance or add effects the

sound of the sources on stage.

21

Single Speaker Cabinets

Single Speaker Cabinets ultimately reproduces tone as sound waves in the air—which are what reaches

the listener’s ear, or a studio microphone.

Position of speaker cabinets on auditorium plan

There are 8 speakers placed at the front of the stage. Instead of placing them on the floor, the speakers

are placed elevated on stage platform so that the high frequencies project over the heads of the audience

members closest to the stage. 2 of the speakers are placed slanted to the left and right to balance the

sound waves in the auditorium.

22

Line Array Speakers

A line array speaker is a loudspeaker system that is made up of a number of usually

identical loudspeaker elements mounted in a line. The distance between adjacent drivers is close enough

that they constructively interfere with each other to send sound waves with a more evenly distributed

sound output pattern.

Position of speakers

There are 2 of these speakers placed in the hanging position above the stage on the left and right. These

speakers are curved with the bottom part angled down to provide extra coverage at locations close to

the front of stage, where else the top half will be angled upwards towards the audience at the top

mezzanine floor of the auditorium.

23

Stage Monitor Speakers

A stage monitor is a type of speaker used on stage in auditoriums and halls where accurate audio

reproduction is crucial. These speakers help amplify the sound when acoustic instruments or voice are

used, allowing the performers on stage to hear themselves.

Position of studio monitors on auditorium plan

There are 2 of these speakers placed in front of the stage by the stairs. They are placed on the ground,

allowing it to project sound towards the stage, helping musicians on stage to focus and monitor the

audio, allowing acoustic instruments and vocals to be heard over electronic instruments and drums.

24

Possible Noise Intrusions

Noise intrusion on fifth floor plan

The possible noises that could affect the auditorium is the lift lobby and the auditorium lobby where

guests and users gather or enter the auditorium.

Noise intrusion on sixth floor plan

The other possible noises could be from the lobby of the mezzanine floor where people gather or first

enter the auditorium.

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SOUND PROPAGATION Sound propagation (or sound path) shows the movement of sound traveling. During the propagation

of sound, these sound waves can be reflected, refracted, diffracted, or attentuated by the medium.

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Sound path in section

Sound path in plan

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Sound Shadow Area

Sound shadow is an acoustic defect where an area through which sound waves fail to propagate. The

sound shadow area in this auditorium is the seating area located under the balcony.

Sound shadow area shown in section

The balcony cantilevers over the seating area on the fifth floor of the building, making the jutted out

structure a obstruction, blocking sound waves from entering the region.

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Solution

Single speakers are added on the ceiling at the bottom of the balcony, projecting sound towards the

audience in the sound shadow area, preventing sound shadowing, thus allowing them to receive the

sound waves.

Location of additional single speakers in floor plan and reflected ceiling plan

Sound shadow area solved shown in section

29

Sound Reflection

Sound reflection occurs when a wave reaches the boundary between objects, part of the waves

undergoes reflection and another part undergoes transmission across the boundary. Despite he fact that

auditoriums typically avoid using hard and smooth materials in the construction of their inside halls,

these reflective surfaces may still be of use to distribute and reinforce sound.

Ceilings

Tilted Ceiling

The ceiling of the auditorium is irregular, and properly tilted to allow more useful reflection of sound.

As opposed to a flat ceiling, the range of useful ceiling reflections is wider.

Tilted ceiling in section

30

Convex Surfaces

Sound is reflected on hard surfaces in the auditorium. They tend to reflect off flat surfaces uniformly,

but when they hit convex surfaces, it causes sound dispersion. Convex reflecting surfaces are lined on

the ceilings and are used to disperse sound.

Convex surfaces in section

31

Walls

Tilted Walls

The irregular walls of the auditorium are properly tilted to allow more useful reflecion of sound. These

walls are lined and covered with fabric panels as well as hardwood. The hardwood surface allow the

reflection of sound within the auditorium.

Tilted walls in plan

32

Sound diffraction

Sound diffraction occurs when the sound waves pass through an opening or around a barrier in their

path, causing a change in direction.

In the case of this auditorium, the balcony that houses the audio console became the obstruction that

splits the sound waves that propagates from the speakers. The sound waves then pass through different

directions, going to different floors of the auditorium.

The cantilevered balcony is a narrow obstruction, giving the sound waves bigger wavelengths.

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REVERBERATION TIME

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On the basis of the presented results, we can see that the reverberation time is 0.6 seconds and is still

within the exceeded normal RT of theater for speech, which is a maximum of 1 second. We have

concluded that the reverberation time obtained is slightly shorter for the function of the room.

Nevertheless it is still considered favorable because the paths of direct sounds waves to audience should

be as short as possible, to reduce sound energy loss.

Area (m2)

Absorption

Coefficient

Absorption Units

Floor

Carpet 2138.4 0.5 1069.2

Parquet Wood 116.34 0.07 8.14

Ceiling

Gypsum Plaster Board 909.4 0.15 136.42

Timber Hardwood 337.1 0.42 141.58

Wall

Left

Fabric Panel 142.1 0.9 127.9

Belian Timber Hardwood 150.3 0.42 63.1

Gypsum Wall Board 24.7 0.08 1.98

Right

Fabric Panel 137.7 0.9 123.9

Belian Timber Harwood 151.4 0.42 63.6

Gypsum Wall Board 24.7 0.08 1.98

Front

Belian Timber Harwood 9.4 0.42 3.9

Gypsum Wall Board 163.9 0.08 13.11

Curtain 236.5 0.4 94.6

Back

Fabric Panel 127 0.9 114.3

Belian Timber Harwood 195.1 0.42 81.9

Glass 2.88 0.1 0.29

Other

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Cushioned Fabric 1948.3 0.64 1246.9

3292.8

Total Volume: 11393 m3